Re: dpkg MD5

Jeremy Stanley <[email protected]> Thu, 7 Nov 2024 23:37:41 +0000

Newsgroups	gmane.linux.debian.devel.security
Message-ID	<[email protected]>

On 2024-11-07 16:45:54 -0500 (-0500), David Campbell wrote:
[...]
> dpkg currently uses MD5 to verify packages, but MD5 is considered
> insecure, why not switch to SHA256 (and also update lintian)?
[...]

MD5 is considered insecure to collision attacks, but mounting one
would require that the creator of the original file intentionally
pick content that can hash to the same value as some malicious
content (and even that is nontrivial, but let's set that aside for
the moment).

https://en.wikipedia.org/wiki/Collision_attack

What you're probably worried about is preimage resistance of the
algorithm (and in particular, second preimage resistance, which is
what keeps some random attacker from creating a file which hashes to
the same value as a known good file).

https://en.wikipedia.org/wiki/Preimage_attack

MD5's preimage resistance is not in question presently, that I've
heard, and it would be pretty big news in the cryptography community
if it were.

> Please, include my email address in the CC if you respond to this
> message. I am not subscribed to the mailing list.
[...]

Sorry, GMail doesn't accept messages from my mailserver, and I'm not
going to bother jumping through hoops just to appease them. Anyone
who's interested in Debian security matters should subscribe to the
mailing list or read its archives in a Web browser at the very
least.
-- 
Jeremy Stanley

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